KR100768509B1 - encryption and decryption device in wireless portable internet system, and method thereof - Google Patents

Abstract

The present invention relates to a device for encrypting and decrypting a wireless portable Internet system and a method thereof.

In a wireless portable Internet system, a terminal and a base station share an encryption key through a key distribution process, and encrypt and transmit a message by using the same. In this case, a first initial value for encryption is generated based on information shared between the terminal and the base station in a wireless section, and the message is encrypted and transmitted based on the first initial value and the encryption key. In addition, the terminal and the base station generates a second initial value for decryption based on information shared in the wireless section, and decrypts the encrypted message based on the second initial value and the encryption key. Here, the first initial value and the second initial value are the same.

Therefore, stable encryption and decryption can be performed without transmitting an initial value for encryption, and the size of a transmission frame can be reduced.

Wireless Cellular Internet, Encryption, Decryption, Initial Value Generation, Zero Hit Counter

Description

Encryption and decryption device in wireless portable internet system, and method

1 is a schematic diagram showing the structure of a wireless portable Internet system according to an embodiment of the present invention.

2 is a diagram illustrating the structure of an encryption and decryption apparatus according to an embodiment of the present invention.

3 is a flowchart illustrating an encryption and decryption process according to an embodiment of the present invention.

4 is a structural diagram of an initial value generating unit according to a first embodiment of the present invention.

5 is a structural diagram of a MAC PDU according to an embodiment of the present invention.

6 is a flowchart illustrating a process of generating an initial value according to a first embodiment of the present invention.

7 is an exemplary view schematically showing the process shown in FIG.

8 is a structural diagram of an initial value generating unit according to a second embodiment of the present invention.

9 is an exemplary view illustrating an operating state of a zero hit counter according to an exemplary embodiment of the present invention.

10 is a flowchart illustrating a process of generating an initial value according to a second embodiment of the present invention.

11 is an exemplary view schematically showing the process shown in FIG. 10.

12 is a structural diagram of an initial value generating unit according to a third embodiment of the present invention.

13 is an exemplary diagram illustrating an operation relationship between a zero cycle number and a zero heat counter according to an exemplary embodiment of the present invention.

14 is a flowchart illustrating an initial value generating process according to a third embodiment of the present invention.

15 is a conceptual diagram illustrating an initial value generating process according to a fourth embodiment of the present invention.

The present invention relates to an encryption technology in a wireless portable internet system, and more particularly, to an encryption and decryption apparatus and a method for secure transmission and reception of a message in a wireless portable internet system.

In the mobile communication system, the wireless portable Internet is a next-generation communication method that further supports mobility to a short-range data communication method using a fixed access point like a conventional wireless LAN. Various standards have been proposed for the wireless mobile Internet, and international standardization of the mobile internet is actively being conducted in IEEE 802.16. Here, IEEE 802.16 is basically a standard that supports Metropolitan Area Network (MAN), and refers to an information communication network covering an intermediate area between a local area network (LAN) and a wide area network (WAN). In particular, the IEEE 802.16e group is releasing a specification to support MAN having the purpose of serving mobile terminals. In Korea, some of the functions of the IEEE 802.16d standard and the IEEE 802.16e standard are adopted by the TTA as a standard for wireless portable Internet (aka WiBro) to provide services.

In such a wireless portable Internet system, various services are provided to a user, and messages are encrypted and transmitted and received for the purpose of preventing information leakage or system disturbance by a third party. That is, the base station or the terminal transmits a message and data using a predetermined resource, and the receiving side decodes the message and data. In this case, a message or data to be protected using encryption is called plaintext (plaintext), and the encryption and conversion of plaintext is called ciphertext (暗號 文, ciphertext). The process of converting plain text into cipher text is called encryption, and the process of decrypting cipher text back to plain text is called decryption.

The encryption algorithm used in the wireless portable Internet is based on encrypting the encryption targets (messages and data) on a block basis. The block cipher algorithm transforms a fixed size input block into a fixed size output block using an encryption key, where each bit of the output block is affected by all the bits of the input block and the key. A conventional block encryption algorithm is a Data Encryption Standard (DES) using a 56 bits key, and an Advanced Encryption Standard (AES) using a 128 bits key that supplements the stability of the DES.

Since the block cipher algorithm performs encryption and decryption on a 64-bit or 128-bit block basis, a plurality of blocks must be processed when encrypting and decrypting general data. In this case, a method of giving an association or dependency between each block is called a mode, and a commonly used mode is an electronic code book (ECB) mode, a cipher block chaining (CBC) mode, and a counter with CBC-MAC (CCM) mode. And CTR (Counter) mode. Each mode is used in the direction of increasing cryptographic security with proper consideration of advantages and disadvantages.

ECB mode has the disadvantage that the encryption ratio is reduced by encrypting and decrypting each block independently in the simplest manner. Accordingly, the CBC mode, the CCM mode, the CTR mode, etc. are mainly used to increase the cryptographic ratio, and these modes use a predetermined initial value for each cryptographic application unit. That is, an initial value is set for each message, and the transmitting side encrypting and transmitting the message and the receiving side decrypting the message perform encryption and decryption on the same message using the same initial value.

To this end, a field for transmitting an initial value is added to the transmitted message. Specifically, in the CCM mode or the CTR mode for the AES block algorithm, a 4-byte field is added to the message, and an initial value is recorded and transmitted in the corresponding field. This has the disadvantage of reducing data efficiency relatively when the message is small. In addition, there is a problem that the bandwidth usage efficiency is reduced.

Meanwhile, in the CBC mode for the DES block algorithm, encryption is performed using an initial value exchanged during the key distribution process, that is, a CBC IV (Initial vector) value. Specifically, an XOR operation is performed on the CBC IV value and the PHY frame value for each frame. Block encryption is performed based on the result obtained. Since a medium access control (MAC) protocol data unit (MAP) is transmitted to a resource allocated for each frame, an initial value of each MAC PDU may be changed to satisfy the required cryptographic ratio in the CBC mode. However, since the frame value is changed every frame, the result value obtained by the XOR operation is also changed frame by frame. Accordingly, cryptographic performance is poor because there is a case in which the initial value for each MAC PDU cannot be met. .

Therefore, the technical problem to be achieved by the present invention is to solve the conventional problems as described above, the initial value for encryption at the transmitting and receiving side, even if additional information for encryption when transmitting and receiving a message in a wireless portable Internet system To provide an apparatus and method for performing encryption or decryption by generating a.

In addition, the technical problem to be achieved by the present invention is to generate the same initial value in the encryption device and decryption device using the information given for each message, so that the encryption and decryption can be performed respectively.

In addition, the technical problem to be achieved by the present invention is to generate an initial value that satisfies the requirements for maintaining the encryption ratio by changing the input value in the encryption and decryption process for each message without an optional value field added for each message.

Another object of the present invention is to generate an initial value that satisfies the requirement for maintaining a password ratio while minimizing the size of an arbitrary value field added for each message.

An initial value generating method according to an aspect of the present invention for achieving the above technical problem, in a wireless portable Internet system in which the terminal and the base station shares an encryption key through a key distribution process, encrypting messages transmitted and received between the terminal and the base station A method of generating an encryption initial value required to perform a decryption or decryption, the method comprising: a) extracting first information shared by the terminal and a base station in a wireless section; b) extracting predetermined second information from the message; And c) generating the encryption initial value based on at least one of the first information and the second information.

According to another aspect of the present invention, a method for generating an initial value includes encryption required for encrypting or decrypting a message transmitted and received between the terminal and the base station in a wireless portable Internet system in which the terminal and the base station share an encryption key through a key distribution process. A method of generating an initial value, the method comprising: a) determining a frame number to be broadcast for each frame; b) extracting the header of the message to determine header information; c) determining an identifier for the terminal; And d) generating an initial value for encryption based on the frame number, the header information, and the terminal identifier.

In this case, the terminal and the base station may additionally share a fixed initial value in the key distribution process. And d) performing logical operation on the frame number, header information, and terminal identifier with the fixed initial value to obtain an initial value plaintext; And generating the encryption initial value by processing the initial plain text according to the encryption key.

According to another aspect of the present invention, a method for generating an initial value is required in a wireless portable Internet system in which a terminal and a base station share an encryption key through a key distribution process. A method of generating an encryption initial value, the method comprising: a) determining a frame number to be broadcast per frame; b) extracting the header of the message to determine header information; c) determining an identifier for the terminal; d) obtaining a count value indicating a number of times the frame number becomes a zero hit; And e) generating an initial value for encryption based on the frame number, the header information, the terminal identifier, and the count value.

In this case, the terminal and the base station may additionally share a fixed initial value in the key distribution process. And e) performing logical operation on the terminal identifier and the count value to obtain an operation value; Logically calculating the frame number, the header information, and the operation value with the fixed initial value to obtain an initial value plaintext; And generating the encryption initial value by processing the initial plain text according to the encryption key.

In addition, the encryption apparatus according to another aspect of the present invention, in a wireless portable Internet system in which the terminal and the base station share the encryption key through a key distribution process, the device for encrypting messages transmitted and received between the terminal and the base station, An initial value generator configured to generate an encryption initial value for encryption on the message based on information shared by a base station in a wireless section; And an encryption unit for encrypting the message based on the encryption initial value and the encryption key.

In a decoding apparatus according to another aspect of the present invention, in a wireless portable Internet system in which a terminal and a base station share an encryption key through a key distribution process, in a device for decoding an encrypted message, the terminal and the base station have a wireless section. An initial value generator configured to generate an encryption initial value for decryption on the message based on the information shared by the user; And a decryption unit for decrypting the message based on the encryption initial value and the encryption key, wherein the generated encryption initial value is the same as the initial value used when encrypting the message.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention.

In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

In addition, the term module described herein refers to a unit for processing a specific function or operation, which may be implemented in hardware or software, or a combination of hardware and software.

1 is a view schematically showing the structure of a wireless portable Internet system according to an embodiment of the present invention.

The wireless portable Internet system basically includes a subscriber station 100, a base station 200, 210 (optionally, "200" is assigned as a representative number for convenience of description), packet access routers 300, 310 connected to the base station, And an authentication server (AAA) 400 that is connected to packet access routers (PARs 300 and 310) and performs authentication for the subscriber station (100). In addition, a home agent (HA) 500 may be further included.

A base station is installed in, for example, a dense urban area and manages several terminals, and a packet access router manages a plurality of base stations to form a hierarchical structure.

In such a wireless portable Internet system, a wireless link connection, basic function negotiation, authentication, registration, handoff, traffic connection setting function, etc. are performed according to the interworking of the subscriber station 100, the base station 200, and the packet access router 300. do. In this case, the base station 200 processes a signal transmitted from the terminal 100 or the packet access router 300 and transmits the signal to the packet access router 300 or the terminal 100, respectively, and the packet access router 300 includes a plurality of The base station 200 is managed to perform handoff control and mobile IP functions.

Meanwhile, the subscriber station 100 and the base station 200, 210 start communication and negotiate an authentication mode for authentication of the subscriber station 100, and perform an authentication procedure of a selected method according to the negotiation result.

In a wireless portable Internet system having such a feature, an encryption and decryption apparatus according to an embodiment of the present invention includes a message (wherein the message includes all types of messages that can be transmitted and received on the wireless portable Internet, such as a message including data). The encryption and decryption are performed based on a key holding a predetermined value at the time of encryption or decryption and an initial value whose value varies for each message.

2 is a structural diagram of an encryption and decryption apparatus according to an embodiment of the present invention.

As shown in FIG. 2, the encryption apparatus 10 according to an embodiment of the present invention includes an initial value generator 11 and an encryption unit 12, and inputs plain text (PT) input text. Output it by converting it into cipher text (CT).

In the embodiment of the present invention, the encryption unit 12 performs encryption on a block basis according to the CBC mode, performs an exclusive OR operation on the generated initial value and the input plaintext, and then encrypts the output based on the encryption key and outputs the encrypted text. After that, the plaintext of the block to be input is subjected to an exclusive OR operation with the ciphertext of the previous block, and then encrypted and output based on the encryption key. However, the present invention is not limited to this CBC mode but can be applied to other cryptographic modes that perform encryption using initial values.

Meanwhile, the decryption apparatus 20 includes an initial value generator 21 and a decryptor 22. The decryption apparatus 20 receives the cipher text transmitted based on the frame, converts the received cipher text back to plain text, and outputs the cipher text. At this time, the initial value generating unit 21 generates an initial value identical to the initial value used when processing the received cipher text, and the decrypting unit 22 converts the encryption key and the message which are kept constant during the decryption process. Based on this, the ciphertext inputted is decrypted into plain text.

The initial value generators 11 and 21 used in the encryption apparatus 10 and the decryption apparatus 20 generate the initial value using information shared by the base station and the terminal in the wireless access section, including the frame number. .

Based on this structure, an encryption and decryption method according to an embodiment of the present invention will be described.

3 is a flowchart illustrating an encryption and decryption method according to an embodiment of the present invention. In FIG. 3, an example of a base station is used as a transmitting side for encrypting and transmitting a message, and an example of a terminal as a receiving side for receiving and decrypting a message transmitted after being encrypted is not necessarily limited thereto.

After a connection is established between the terminal 100 and the base station 200 and an authentication procedure is performed, a key distribution process is performed, and the terminal and the base station maintain a constant key during the encryption process, that is, an encryption key (TEK). Key). In addition, in the key distribution process, the fixed initial value used for block encryption is shared (S10). This initial value is fixed to a value shared by the terminal and the base station in the key distribution process. Subsequently, when the message is encrypted and decrypted, it is different from the initial value generated by each device 10 or 20 according to an embodiment of the present invention. Therefore, the initial value shared in the key distribution process is used to clarify the distinction. The initial value, which is newly generated for each message in each device 10 and 20, is referred to as the "fixed initial value".

Meanwhile, the terminal 100 and the base station 200 encrypt and transmit or receive and decrypt a message based on an encryption key (TEK) shared with each other in a key distribution process.

In detail, as shown in FIG. 3, when the transmitter, for example, the base station 200 intends to transmit a message, the initial value generator 11 of the encryption apparatus 10 may have an initial value having a different value for each message. An encryption initial value is generated (S20). In particular, an encryption initial value is generated using information shared by a base station and a terminal in a wireless access section including a frame number and the like.

Thereafter, the encryption unit 12 encrypts and transmits the plain text input based on the key maintained constant in the encryption process, that is, the encryption key and the generated encryption initial value (S30 to S40).

Meanwhile, the receiving device 20 that receives the message including the encrypted plain text, that is, the cipher text, that is, the decryption apparatus 20 of the terminal 100 uses the information shared with the base station for the received message. It generates (S50). The encryption initial value generated at this time has the same value as the encryption initial value used when the base station encrypts the message.

Next, the decryption unit 22 decrypts the cipher text included in the message based on the encryption initial value generated for the message and the encryption key that is kept constant in the decryption process (S60).

According to the embodiment of the present invention, even if the initial value for encryption or decryption is not transmitted separately when the message is transmitted, the initial value is generated based on the information on the message shared by the transmitting side and the receiving side, and the encryption and decryption are performed. can do.

Next will be described in detail for generating an initial value for encryption and decryption according to an embodiment of the present invention.

First, a method of generating an initial value in encryption and decryption according to a first embodiment of the present invention will be described. In the first embodiment of the present invention, an encryption initial value for encryption and decryption is generated based on predetermined information in a header of a message and information on a frame in which the message is transmitted. In this case, the encryption initial value is generated by further considering an identifier of an object of the message.

4 is a structural diagram of the initial value generators 11 and 21 according to the first embodiment of the present invention.

The initial value generators 11 and 12 according to the first embodiment of the present invention input the frame number determination module 111 for determining information of the frame to which the message is transmitted, that is, the frame number, as shown in FIG. 4. A header extracting module 112 for extracting a header portion of the message, an identifier determining module 113 for determining an identifier for a target of the message, and header information, a frame number, and an identifier of the extracted message; A logical operation module 114 for performing logical operation with the fixed initial value obtained in step S and outputting the result as a plain text for generating an encryption initial value, and generating the encryption initial value by processing the plain text for generating an initial value with an encryption key. Module 115.

Messages are processed and transmitted in units of PDUs, and each PDU is delivered to the MAC layer by adding a header and a trailer, and composed of MAC frames in the MAC layer. The structure of the MAC PDU is shown in FIG. The MAC PDU includes a generic message header (GMH) field, data (payload), and CRC field for error checking, as shown in FIG. 5.

The GMH field stores message related information and includes a type field indicating a message type, a length field LBN, a header check sum (HCS) field, and a connection identifier field (CID).

The length field may be, for example, 2 bytes in size, and stores information on the length of the PDU. Each PDU has a different length, and the receiving side can check the data size based on the length information.

The HCS field may be, for example, 1 byte in size, and this is a field for checking an error of a header. The receiver determines whether the header is valid based on the information of the HCS field, and processes the received PDUs based on the information stored in the header.

The size of the GMH field is fixed to, for example, 6 bytes, but each field of the GMH is configured according to the purpose. 5 shows a header of a general message. Of the GMH fields used in the embodiments, the length field and the HSC field are most likely to change their values for each PDU. Therefore, in the embodiment of the present invention, the value is changed for each message and an initial value is generated using the values of the length field of the GMH and the HCS field, which are information shared between the base station and the terminal. However, the present invention is not limited thereto, and other field values of the GMH may be used, and thus values recorded in at least one field constituting the GMH are used.

The header extraction module 112 extracts the header of the message, that is, extracts the GMH field of the MAC PDU, and provides the logic operation module 114 with information of the extracted GMH field (length field and information of the HCS field). .

The frame number determination module 111 determines the information of the PHY SYN field of the MAC frame corresponding to the message and provides the information to the logic operation module 114. In the PHY SYN field, a value for frame synchronization is stored, and this value is varied and broadcast for each frame. The value of this PHY SYN field is called "frame number" for convenience of description. The frame number may be sequentially increased or decreased. In the PHY SYN field, for example, 3 bytes may indicate a frame number, and 1 byte may indicate a length of a frame.

The identifier determination module 113 is an identifier for the target of the message. In the embodiment of the present invention, since the encryption and decryption of the message transmitted and received between the base station and the terminal, the MAC address of the terminal is used as an identifier, but is not necessarily limited thereto.

The logical operation module 114 logically outputs the information of the GMH field, the frame number stored in the PHY SYN field, and the identifier, that is, the terminal MAC address. Specifically, the result of calculating the exclusive OR with the fixed initial value and the GMS field information, the frame number, and the terminal MAC address is output. Although the logical operation module 114 exclusively ORs the frame number and the terminal MAC address with the fixed initial value, the logical operation module 114 is not limited thereto and may output only the frame number with the fixed initial value as the result value.

The generation module 115 processes the value provided from the logical operation module 114 as a predetermined key, that is, an encryption key, and outputs the value as the encryption initial value IV.

Next, an initial value generating process according to the first embodiment of the present invention will be described based on the initial value generating unit having such a structure.

6 is a flowchart illustrating a process of generating an initial value according to an embodiment of the present invention, and FIG. 7 is an exemplary diagram illustrating the process.

When a base station or a terminal side wants to transmit a predetermined message to a counterpart node, the message is processed in units of MAC PDUs, and a GMH field is added to each PDU. The MAC PDU processed as described above is input to the encryption apparatus 10 as shown in FIG. 2. Hereinafter, such a MAC PDU is referred to as an "input message", and the data of the PDU as an input message is referred to as "input plaintext".

Meanwhile, the initial value generator 11 of the encryption apparatus 10 generates an initial value for the input message. In detail, as shown in FIGS. 6 and 7, the frame number of the frame to transmit the PDU is determined from the PHY SYN field (S100), the GMH field of the header of the input message is extracted, and the MAC of the UE corresponding to the message is also extracted. The address is determined (S110 to S130). Then, the information of the GMH field, the frame number, and the terminal MAC address are subjected to an exclusive OR operation with a fixed initial value and the value is output as a plain text for generating an initial value, that is, an initial value plain text (S140 to S150) (FIG. 7A ) Reference). On the other hand, when outputting the initial plain text, the terminal identifier, that is, the terminal MAC address, may not be considered, and only the information of the GMH field and the frame number may be ORed together with the fixed initial value and may be used as the plain text for generating the initial value.

The initial plain text output as described above may be used as an initial value (IV) for encryption, but in an embodiment of the present invention, the block cipher algorithm is performed using an encryption key (TEK) without using the initial plain text as it is, Accordingly, the output value is finally used as an initial value IV for encryption (S160) (see FIG. 7B). Here, AES is used as the block cipher algorithm, but is not limited thereto.

The initial value IV generated as described above is input to the encryption unit 12, and the encryption unit 12 uses the initial value IV and the encryption key TEK to be input, that is, the input plaintext of the input message. And print it out.

The input message including the ciphertext output as described above is processed and transmitted as a MAC frame. In this case, related information (frame number, terminal identifier, etc.) is stored in the header of the transmission frame.

The receiving side receives such a frame and delivers it to the decoding apparatus 20. The initial value generator 21 of the decoding apparatus 20 extracts the PHY SYN field from the received frame, determines the frame number based on the received frame number, and determines the destination address. The GMH field of the input message included in the frame is extracted. After that, as in the initial value generation process in the encryption step described above, an exclusive logical operation is performed on the frame number, the destination address and the GMH field with the fixed initial value, and the encrypted value is encrypted with the encryption key to generate an initial value for decryption. do. In this case, even if the initial value used for encryption is not included in the transmission frame, an initial value having the same value as the initial value used for encryption can be generated based on the information included in the transmission frame. Therefore, decryption is performed based on the initial value which is the same value as the initial value used at the time of encryption.

According to this first embodiment, even if the initial frame for decryption is not included in the transmission frame, encryption and decryption generate the same initial value to perform encryption and decryption, thereby significantly reducing the size of the transmission frame and providing stable encryption. Can be made.

In addition, an initial value is generated based on a value that is variable for each PDU (eg, information of a GMH field and a PHY SYN), so that the initial value is varied for each message to satisfy a cryptographic degree required in a predetermined encryption mode (eg, CBC mode). have.

Next, an encryption apparatus and an initial value generation for decryption according to the second embodiment of the present invention will be described. In the following description, for the convenience of description, detailed descriptions of the same functions as those of the first embodiment and components that perform the functions will be omitted.

8 is a structural diagram of an initial value generating unit according to a second embodiment of the present invention.

The initial value generators 11 and 21 according to the second embodiment of the present invention are the same as the first embodiment, as shown in FIG. 8, the frame number determination module 111, the header extraction module 112, Including the identifier determination module 113, the logic operation module 114, and the generation module 115, unlike the first embodiment, a zero hit counter (ZHC) 116 is further added to compensate for the frame number. Include. The zero hit counter 116 is sequentially incremented for each frame, and is a counter indicating how many times the value of the frame number (PHY SYN) field broadcasted for each frame in the radio access section teaches "0".

In general, the frame number is used as a predetermined value within a range of a predetermined value, for example, 0 to M (where M is a natural number of 1 or more), and is used repeatedly within the range. That is, frame numbers are sequentially 0, 1, 2,... It increases to M and then starts again from zero and changes its value to M so that the frame number becomes "0" at every instant. Thus, the frame number being "0" is called "zero hit." If the frame number is changed from 0 to M as the frame period, the frame number becomes zero hit at every predetermined time, that is, the frame number has the same value for each frame period. Accordingly, when the initial value IV is generated based on the frame number having the same value every predetermined period, the same initial value may be generated.

Therefore, in the second embodiment, a zero hit counter is used to count how many times the value of the PHY SYN field, which is a field to be broadcast in the radio access section, is sequentially increased for each frame. Therefore, the count value of the zero hit counter 116 is varied every time a zero hit is generated. 9 illustrates an operation process of a zero hit counter according to a second embodiment of the present invention. The zero hit counter 116 is initialized to "0" at the time of key distribution, as shown in FIG. 9, and then increases by +1 whenever the value of the PHY SYN field that is variable within the range of 0 to M becomes "0". do.

The concept of the zero hit counter can be applied to various objects having a zero value as well as the PHY SYN field. That is, the zero hit counter is the number of times the target field has a value of zero. In particular, in a condition in which the target field is sequentially increased, instead of calculating a zero hit counter each time, a formula of calculating a zero hit counter at an instant i that satisfies a condition may be used. In this case, the same result can be obtained at the time of calculating the zero hit counter each time and at the instant i when the condition is met.

Let N (i) be the value of the target field at the i th instant and ZHC (i) be the value of the zero hit counter. In this case, the equation for calculating the value of the zero hit counter is shown in Equation 1 below.

The moment of calculating the value of the zero hit counter can be divided into two. One is when the target field becomes zero and the other is when the message is received. In general, when the target field becomes 0, the zero hit counter satisfies all conditions. However, the receiver side (terminal) receiving the target field broadcast in the wireless access section loses the case where the target field value is 0. As a supplement to the case, the zero hit counter can be calculated at the moment of receiving the message.

FIG. 9 illustrates a case in which a target field is a PHY SYN field. In FIG. 9, the UE receives a second frame with a PHY SYN field of “0” and subsequently loses a frame with a PHY SYN field of 0. FIG. The case is shown. In this case, the UE may increase the value of the zero hit counter by applying the value of the PHY SYN field to Equation 1 at the time of receiving the message (3th event).

As described above, according to the second embodiment of the present invention, a count value is generated by counting the moment when the value of the target field, that is, the broadcast PHY SYN field, becomes zero using a zero hit counter, or at the moment the message is received, the equation Generate a count value according to 1, and use this count value when generating an initial value for encryption.

Meanwhile, the initial value generator generates an initial value based on the count value of the zero hit counter in addition to the GMH field information, frame number, and terminal MAC address described above, so that the same initial value is not generated for each PDU.

10 is a flowchart illustrating a process of generating an initial value according to a second embodiment of the present invention, and FIG. 11 is a diagram illustrating an example of generating an initial value according to the process.

10 and 11, when an input message is input, the initial value generator 11 of the encryption apparatus 10 determines the frame number from the PHY SYN, as in the first embodiment, and determines the input message. The GMH field is extracted, and the MAC address of the terminal corresponding to the message is determined.

However, unlike the first embodiment, after determining the frame number, the zero hit counter 116 checks whether the frame number is "0", and if it is "0", increases the count value by a predetermined value. Initially, the count value of the zero hit counter is "0", and this value is maintained during the frame period of the frame number. However, when the frame period has elapsed and the frame number is repeated again, the count value of the zero hit counter is increased by a predetermined value to be, for example, "1" (S200 to S240).

The initial value generator 11 performs an exclusive OR operation on the count value of the zero hit counter 116 and the terminal MAC address first to obtain an operation value (S250), the obtained operation value, information of the GMH field, and An exclusive OR of the frame number is performed on the fixed initial value to obtain a plain text for generating an initial value, that is, an initial value plain text (S260) (see FIG. 11A). In this case, the initial value generator 11 may use the count value only as a calculation value without considering the terminal identifier (MAC address).

The initial plain text obtained as described above is processed by the encryption key TEK, output as an initial value IV for encryption, and input to the encryption unit 12 (S270) (FIG. 11B). Reference).

Thereafter, the encryption unit 12 encrypts and outputs the input plaintext based on the initial value IV and the encryption key TEK, and the ciphertext is processed as a MAC frame and transmitted.

The decryption apparatus 20 on the receiving side also generates an initial value as described above, and decrypts the cipher text of the received transmission frame based on the initial value.

According to the second exemplary embodiment, even when the frame number is repeated for each predetermined period, the count value of the zero hit count value is variable, and an initial value is generated using the variable count value and the plurality of information. The branch may generate an initial value to perform secure encryption and decryption.

In addition, as in the first embodiment, it is possible to satisfy the required encryption ratio while efficiently using the bandwidth of the transmission frame.

Next, an initial value generation for encryption and decryption according to a third embodiment of the present invention will be described. Hereinafter, for convenience of description, detailed descriptions of components that perform the same functions or perform the same functions as the first and second embodiments will be omitted.

12 is a structural diagram of an initial value generating unit according to a third embodiment of the present invention.

The initial value generators 11 and 21 according to the third embodiment of the present invention are the same as the second embodiment, as shown in FIG. 12, the frame number determination module 111, the header extraction module 112, The counter correction unit 117 includes an identifier determination module 113, a logic operation module 114, a generation module 115, and a zero hit counter 116, but unlike the second embodiment, the counter correction unit 117 compensates for the count value. It further includes.

The broadcast frame is lost due to various factors of the radio section. Therefore, when zero hits are counted using the PHY SYN field as a target field, a frame including the field may be lost, and a malfunction may occur such that the zero hit counter may not count zero hits.

Therefore, in the embodiment of the present invention, in order to prevent such an error, the node broadcasting the PHY SYN field, that is, the base station, counts the instant when the value of the PHY SYN field becomes "0" and broadcasts the value every predetermined time. The value broadcast in the base station as such is referred to as "zero cycle number (ZCN)". The initial value of the zero cycle number may be arbitrarily set and is changed from the initial value to a predetermined value according to the zero hit count. The terminal corrects the value of the zero hit counter generated by itself by using the zero cycle number broadcasted in this way and uses the generated initial cipher value.

Specifically, the counter correction unit 117 checks the zero cycle number broadcasted, compares the count value provided from the zero hit counter 116 with the zero cycle number, verifies the count value, and optionally counts the count value accordingly. Calibrate 13 shows an example of a verification and correction function of a zero hit count value using a zero cycle number.

The base station 200 broadcasts a zero cycle number at a predetermined time point, and particularly, informs the zero cycle number in a frame for distributing an encryption key (TEK), and then the counter corrector 117 of the terminal 100 broadcasts the frame. Stores the value of the zero cycle number (eg 6). Then, a new zero cycle number broadcasted every predetermined time is received from the base station, and a difference between the received zero cycle number (eg, 7) and the stored zero cycle number (eg, 6) is calculated. The difference between the calculated zero cycle numbers and the count value of the zero hit counter 116 are compared to determine whether a frame including the PHY SYM field is lost.

Specifically, when the difference between the zero cycle numbers is not "0", it means that zero hit of the frame number is generated and the zero cycle number is changed. Therefore, if the count value of the zero hit counter does not change even though the difference value is not "0", it is determined that frame loss has occurred and the count value of the zero hit count is changed according to the difference value. For example, assume that the value of the zero cycle number previously received and stored as shown in FIG. 13 is "6", and the count value of the zero hit counter measured at this time is "0". When the value of the zero cycle number received at a predetermined time point is "7", the zero cycle number of the frame number is changed once when zero hit of the frame number occurs once. However, if the count value of the zero hit counter is not changed and the old value "0" is maintained, this is an error state in which the terminal does not receive a frame of the PHY SYN field including the frame number.

Accordingly, the counter corrector 117 matches and stores the zero cycle number and the count value of the zero hit counter measured at each time when the zero cycle number is received. And a difference value (first difference value) between the current zero cycle number and the stored previous zero cycle number, the count value of the current zero hit counter, and the count value of the zero hit counter matched with the previous zero cycle number. According to the relationship between the difference values (second difference values), the frame loss error is determined. If it is confirmed that an error has occurred, the count value of the zero hit counter is changed according to the first difference value and corrected.

The initial value generator then generates an initial value based on the count value of the zero hit counter, which is selectively corrected based on the zero cycle number, in addition to the GMH field information, the frame number, and the terminal MAC address. Therefore, the same initial value may not be generated for each PDU.

14 is a flowchart of an initial value generating process according to a third embodiment of the present invention.

As shown in FIG. 14, when an input message is input, the initial value generator 11 of the encryption apparatus 10 determines the frame number from the PHY SYN, as in the second embodiment, and the zero hit counter 116. Determines whether the frame number is "0" and increases the count value when the frame number is "0", and maintains the old value without increasing the count value when the frame number is not "0" (S300 to S310). . Thereafter, the counter corrector 117 selectively corrects the count value of the zero hit counter as described above based on the broadcast zero cycle number (S330). The GMH field of the input message is extracted, and the MAC address of the terminal corresponding to the message is determined (S340 to S360).

The initial value generating unit 11 performs an exclusive OR operation on the count value of the zero hit counter 116, which is selectively corrected as described above, with the terminal MAC address, which is the terminal identifier, to obtain an operation value, and obtains the obtained operation value and information on the GMH field. , The frame number is subjected to an exclusive OR operation with a fixed initial value to obtain an initial value plaintext (S370 to S390). In this case, the initial value generator 11 may use the count value only as a calculation value without considering the terminal identifier (MAC address).

Next, the obtained initial value plaintext is processed according to the encryption key TEK to generate an initial value IV for encryption (S400).

Thereafter, the encryption unit 12 encrypts and outputs the input plaintext based on the initial value IV and the encryption key TEK, and the ciphertext is processed as a MAC frame and transmitted.

The decryption apparatus 20 on the receiving side also generates an initial value as described above, and decrypts the cipher text of the received transmission frame based on the initial value.

According to the third embodiment of the present invention as described above, even if the frame is lost in the radio section, by correcting the zero hit count value by using the zero cycle number broadcast from the base station, by generating the initial value that is variable for each message accurately can do.

Meanwhile, in a general CCM mode and a CTR mode, a nonce field added to a PDU is a field for recording an initial value for encryption for each message. Conventionally, although a temporary field uses 4 bytes, the fourth embodiment of the present invention reduces the size of the temporary field to a minimum and performs initial value generation using the reduced temporary field. This reduced size temporary field is called a "reduced nonce (RN) field". In the fourth embodiment of the present invention, the size of the reduced temporary field is set to 1 byte, but is not limited thereto.

In the fourth exemplary embodiment of the present invention, an encryption temporary value is generated at the transmitting and receiving side by applying the concept of the zero hit counter described above to the decreasing temporary field while transmitting and adding the reduced temporary field for each message.

15 is an exemplary diagram illustrating the concept of a reduced temporary field for generating an initial value according to a fourth embodiment of the present invention. The reduced temporary field (RN) records a MAC PDU, that is, a random value arbitrarily set as a field added per message, which has a length smaller than the existing length, for example, 4 bytes. As an example, assume that the size of the reduced temporary field is 1 byte. In this case, the reduced temporary field has a value of 0 to 256, and "0" repeatedly appears every 256.

Such a reduced temporary field may be selectively applied to the above first to third embodiments. In this case, it is assumed that in the first to third embodiments, a temporary temporary field is added to the message in addition to the header field, the data, and the CRC field.

In the case of the first embodiment, a reduced temporary field may be used instead of the PHY SYN field. In this case, the frame number determination module 111 of the initial value generation unit 11 of the first embodiment functions as a module for determining an arbitrary value of the reduced temporary field. Thus, the initial value generator generates an initial value for encryption as described above using the random number of the reduced temporary field instead of the frame number of the PHY SYN field, the information of the GMH field of the message, and the terminal MAC address that is optionally considered. Messages can be encrypted and decrypted.

In the case of using the reduced temporary field, as in the second embodiment, the concept of the zero hit counter may be applied to compensate for the case where the value of the reduced temporary field is repeated the same, so that the initial value change period may be increased. . In this case, instead of counting zero hits based on the value of the PHY SYN field, the zero hit counter counts the case where the value of the decremented temporary field included in the message is "0". At this time, the zero hit counter operates as a reduced number zero hit counter (RNZHC). The initial value generating unit generates an initial value for encryption as in the second embodiment described above by using the decremented temporary field value and the count value, the GMH field information of the message, and the terminal MAC address to be selectively considered. The message can then be encrypted and decrypted.

In addition, when a frame loss occurs by applying a zero cycle number to the value of the reduced temporary field counted as described above, the count value of the reduced temporary field counted may be corrected.

As described above, when the fourth embodiment using the reduced temporary field is applied to the first to third embodiments, a part of the PHY SYN field may be used as the reduced temporary field RN. For example, when the PNY SYN field is composed of 4 bytes, 1 byte is used as the reduced temporary field (RN) to record an arbitrary value for initial value generation.

In addition, when the reduced temporary field RN according to the fourth embodiment is applied to the third embodiment, the PHY SYN field is reduced and the count value for correcting the reduced temporary field is recorded. (RNZHC). That is, since the value of the reduced temporary field also has the same value every predetermined period as described above, it is necessary to correct this. Therefore, in order to correct the value of the reduced temporary field like the zero cycle number of the third embodiment, the base station may count an arbitrary value recorded in the reduced temporary field and broadcast the random cycle number value. In this case, the PHY SYN field may be replaced with a reduced temporary field RN and an arbitrary cycle number field RNZHC. For example, when the PHY SYN field consists of 4 bytes, the RN field may consist of 1 byte and the RNZHC field may consist of 3 bytes.

In addition, instead of using the reduced temporary field instead of the PHY SYN field in the first to third embodiments, the initial value may be generated by using the PHY SYN field and the reduced temporary field together. That is, an initial value may be generated using an arbitrary value of a reduced temporary field, information of a GMH field, and a terminal MAC identifier that is optionally considered, in addition to the frame number of the PHY SYN field.

For example, in the case of the first embodiment, an exclusive logical OR operation is performed on the frame number of the PHY SYN field and the arbitrary value of the reduced temporary field to obtain a predetermined operation value. The initial value plaintext is obtained by performing an exclusive OR operation on the operation value and the information of the GMH field and a terminal MAC address that is optionally considered, and then obtaining an initial value plaintext, and processing the encryption value to obtain an initial encryption value.

In addition, in the case of the second embodiment, the concept of the zero hit counter may be equally applied to the decremented temporary field and the frame number, respectively, to equally compensate for the case where the values of the decremented temporary field and the frame number are identically repeated. In this case, the value of the zero hit counter may be divided into a first count value indicating zero hit of the decrement temporary field and a second count value indicating zero hit of the frame number, respectively. Accordingly, the initial value generator may generate an initial value for encryption as in the second embodiment described above by using the first and second count values, the information of the GMH field of the message, and the terminal MAC address that is selectively considered. .

Of course, when the frame number of the PHY SYN field and the reduced temporary field are used together in the third embodiment, the cycle number and the number of the reduced temporary field counted in the third embodiment are zero-cycle number. Based on the correction, it can be used to generate an initial value for encryption.

A person skilled in the art may selectively apply the reduced temporary field according to the fourth embodiment to each embodiment based on the first to third embodiments described above, and thus, detailed description thereof will be omitted.

In addition, although the above-described first to fourth embodiments have been described based on the consideration of the terminal identifier (terminal MAC address) when generating the initial value for encryption, the terminal identifier is not considered when generating the initial value as described above. It may be.

The above-described encryption and decryption methods and initial value generation methods may be implemented in the form of a program stored in a computer-readable recording medium. The recording medium may include any kind of recording device that stores data that can be read by a computer. For example, a CD-ROM, a magnetic tape, a floppy disk, and the like may be used. Included is implemented in the form of).

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the embodiment of the present invention described above, the following effects are obtained.

First, even when the wireless portable Internet system does not additionally transmit information for encryption when transmitting and receiving a message, the transmitting and receiving side may generate an initial value for encryption and perform encryption or decryption. Therefore, the size of the message transmission frame is reduced, thereby increasing the bandwidth usage efficiency.

Second, by generating the initial value for the encryption function for each message, it is possible to minimize the size of the temporary field for additional information for the encryption function.

Third, since an initial value having a different value can be generated for each message, the cryptographic algorithm satisfies the minimum requirement for satisfying the cryptographic secret.

Fourth, by using the zero hit counter, it is possible to reduce the probability that the initial values are the same for the same message, and in particular, the probability can be significantly reduced compared to the conventional use of 4 byte temporary fields in the message.

Fifth, by correcting the value of the zero hit counter using the zero cycle number, it is possible to reduce the possibility of an error occurring in the probability.

Sixth, even in the case of using a temporary field having a significantly smaller size than the existing 4-byte temporary field, a zero hit counter is applied to increase the initial value change period, thereby significantly reducing the probability of using the same initial value for each message. have.

Claims (34)

In a wireless portable Internet system in which a terminal and a base station share an encryption key through a key distribution process, a method of generating an encryption initial value required to encrypt or decrypt a message transmitted and received between the terminal and the base station, a) obtaining first information shared by a terminal and a base station in a wireless section; b) extracting predetermined second information from the message; And c) generating the encryption initial value based on at least one of the first information and the second information. The method of claim 1 The first information includes a frame number to be broadcast for each frame. C) generating the initial value of encryption based on the frame number. The method of claim 2, The second information is header information included in the header of the message, C) generating the initial value of encryption based on the frame number and the header information. The method of claim 3, The terminal and the base station share an encryption key and a fixed initial value through a key distribution process, Step c) Logically calculating the frame number and the header information with the fixed initial value to obtain an initial value plaintext; And Processing the initial plain text according to the encryption key to generate the encryption initial value Initial value generation method comprising a. The method of claim 3, The first information further includes a count value indicating the number of times the frame number becomes a zero hit, C) generating the initial value of encryption based on the frame number, header information, and the count value. The method of claim 5 The first information further includes a zero cycle number that is a value that the base station counts and broadcasts the number of zero hits of the frame number, Step c) Selectively correcting the count value based on the zero cycle number; And Generating the encryption initial value based on the frame number, the header information and the optionally corrected count value Initial value generation method comprising a. The method according to claim 5 or 6 The terminal and the base station share an encryption key and a fixed initial value through a key distribution process, Step c) Logically calculating the count value to obtain an operation value; Logically calculating the frame number, the header information, and the operation value with the fixed initial value to obtain an initial value plaintext; And Processing the initial plain text according to the encryption key to generate the encryption initial value Initial value generation method comprising a. The method according to any one of claims 2 to 6 The second information further includes an identifier of the terminal, In the step c), when the encryption initial value is generated, the encryption initial value is generated by additionally considering the terminal identifier. The method according to claim 1 or 2, The message includes a decrement temporary field that includes a predetermined random value, the second information includes the random value, C) generating the initial value of encryption in consideration of an arbitrary value of the reduced temporary field. The method of claim 9, The second information further includes a count value indicating a number of times an arbitrary value of the decrease temporary field becomes a zero hit, C) generating the initial value of encryption by further considering the count value. The method of claim 10, The first information further includes a zero cycle number in which the base station counts and broadcasts the number of zero hits of an arbitrary value of a reduced temporary field, Step c) Selectively correcting the count value based on the zero cycle number; And Generating the encryption initial value based on the frame number, the header information and the optionally corrected count value Initial value generation method comprising a. The method according to claim 1 or 2, The first information is information recorded in a PHY SYN field broadcast for each frame, and the PHY SYN field includes a first field including an arbitrary value and a second cycle in which a zero cycle number indicating the number of zero hits of the arbitrary value is recorded. An initial value generation method that includes a field. The method of claim 12, The first information further includes a count value indicating a number of times an arbitrary value of the first field becomes a zero hit, Step c) Selectively correcting the count value according to an arbitrary cycle number of the second field; And Generating the initial encryption value in consideration of the random value and the count value; Initial value generation method comprising a. The method of claim 6, The correcting step Calculating a first difference between a currently obtained zero cycle number and a previously obtained zero cycle number; Calculating a second difference between the current count value and the previous count value; And Correcting the count value according to the relationship between the first difference value and the second difference value Initial value generation method comprising a. In a wireless portable Internet system in which a terminal and a base station share an encryption key through a key distribution process, a method of generating an encryption initial value required to encrypt or decrypt a message transmitted and received between the terminal and the base station, a) determining a frame number to be broadcast for each frame; b) extracting the header of the message to determine header information; c) determining an identifier for the terminal; And d) generating an initial value for encryption based on the frame number, header information and a terminal identifier Initial value generation method comprising a. The method of claim 15 The terminal and the base station additionally share a fixed initial value in the key distribution process, Step d) Logically calculating the frame number, the header information, and the terminal identifier with the fixed initial value to obtain an initial value plaintext; And Processing the initial plain text according to the encryption key to generate the encryption initial value Initial value generation method comprising a. In a wireless portable Internet system in which a terminal and a base station share an encryption key through a key distribution process, a method of generating an encryption initial value required to encrypt or decrypt a message transmitted and received between the terminal and the base station, a) determining a frame number to be broadcast for each frame; b) extracting the header of the message to determine header information; c) determining an identifier for the terminal; d) obtaining a count value indicating a number of times the frame number becomes a zero hit; And e) generating an initial value for encryption based on the frame number, header information, terminal identifier and the count value; Initial value generation method comprising a. The method of claim 17 The terminal and the base station additionally share a fixed initial value in the key distribution process, Step e) Logically calculating the terminal identifier and the count value to obtain an operation value; Logically calculating the frame number, the header information, and the operation value with the fixed initial value to obtain an initial value plaintext; And Processing the initial plain text according to the encryption key to generate the encryption initial value Initial value generation method comprising a. The method according to any one of claims 3, 15, or 17. And the header information is at least one of information constituting a generic message header (GMH) field. The method of claim 19 The header information is a method of generating an initial value, which is information of a length field indicating a message length and a header check sum (HCS) field for checking an error of a header among GMH fields. In a wireless portable Internet system in which a terminal and a base station share an encryption key through a key distribution process, in an apparatus for encrypting a message transmitted and received between the terminal and the base station, An initial value generator configured to generate an encryption initial value for encryption on the message based on information shared between the terminal and the base station in a wireless section; And An encryption unit for encrypting the message based on the initial encryption value and the encryption key Encryption apparatus comprising a. The method of claim 21, The initial value generator A determining module for determining a value of a predetermined target field; A header extraction module for extracting a header portion of an input message; And a generation module for generating an encryption initial value based on the determined value of the target field and the header information of the extracted message. The method of claim 22, And a zero hit counter for obtaining a count value that is a number of times the value of the target field is zero hits. The method of claim 23, wherein A counter correction unit for obtaining a zero cycle number generated at the base station and selectively correcting the count value based on the zero cycle number Encryption device further comprising. The method according to any one of claims 22 to 24, The initial value generation unit further includes an identifier determination module for determining an identifier for the target of the message, And the generation module generates the encryption initial value in consideration of the identifier. The method according to any one of claims 22 to 24. And the target field is a frame number broadcast from a base station for each frame. The method according to any one of claims 22 to 24. And the target field is a reduced temporary field included in the message. The method according to any one of claims 22 to 24. The target field is a PHY SYN field broadcast for each frame, and the PHY SYN field includes a first field including an arbitrary value and a second field in which a zero cycle number indicating zero hit times of the arbitrary value is recorded. Encryption device. In a wireless portable Internet system in which a terminal and a base station share an encryption key through a key distribution process, in an apparatus for decrypting a message transmitted encrypted, An initial value generator configured to generate an encryption initial value for decryption of the message based on information shared between the terminal and the base station in a wireless section; And A decryption unit for decrypting the message based on the encryption initial value and the encryption key Including, And the generated encryption initial value is the same as the initial value used when encrypting the message. The method of claim 29, The initial value generator A determining module for determining a value of a predetermined target field; A header extraction module for extracting a header portion of an input message; And a generation module for generating an encryption initial value based on the determined value of the target field and the header information of the extracted message. The method of claim 30, And a zero hit counter for obtaining a count value which is a number of times the value of the target field is zero hit. The method of claim 31, wherein A counter correction unit for obtaining a zero cycle number generated at the base station and selectively correcting the count value based on the zero cycle number Decoding apparatus further comprising. 33. The method according to any one of claims 29 to 32, The initial value generation unit further includes an identifier determination module for determining an identifier for the target of the message, And the generation module generates the encryption initial value in consideration of the identifier. 33. The method according to any one of claims 30 to 32, The target field is a frame number broadcast from a base station on a frame-by-frame basis, a reduced temporary field included in the message, and the target field is a PHY SYN field broadcast on a frame-by-first field including an arbitrary value; And a second field in which a zero cycle number indicating the number of zero hits of the arbitrary value is recorded.

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